Radiation-power broadening of the Na-D lines in a vapour cell

We have measured the time-resolved fluorescence spectrum of both Na-D lines in a vapour cell. The atoms were excited with a spectrally broadband pulsed dye laser, tuned to resonance. The width of the Na-D lines turned out to be a linear function of the laser intensity, as is predicted by a simple theory based on lifetime considerations. The experimental results are in quantitative agreement with this theory.